A surface inspecting apparatus can inspect a smaller defect by using a PSL of a smaller particle size. However, the particle size of the PSL is restricted. In the conventional surface inspecting apparatus, therefore, no consideration has been taken as to how to inspect the defect of such a small particle size as is not set in the PSL which will be needed in the near future in an inspection of a semiconductor manufacturing step. The invention has a light source device for generating light which simulated at least one of a wavelength, a light intensity, a time-dependent change of the light intensity, and a polarization of light which was scattered, diffracted, or reflected by an inspection object, and the light is inputted to a photodetector of the surface inspecting apparatus. The smaller defect can be inspected.